Due in part to an aging population that wishes to remain active, arthritis of the knee is approaching epidemic proportions in the U.S. Another factor is obesity, since the knees bear much of increased weight in the body. It is estimated that approximately 750,000 surgical procedures are done in the U.S. each year for knee problems, including total-knee replacements, partial-knee replacements, and arthroscopic procedures.
Quite often, patients treated with knee arthroscopy for arthritis of the knee do very poorly. There are a number reasons for this, but the low rate of success is largely due to the fact that these patients have a small area of their cartilage which is denuded of cartilage and they continue to have pain. Although the area of cartilage eburnation is not large enough to warrant joint replacement procedure, it is large enough to cause continued problems and significant patient dissatisfaction.
Uni-compartmental knee procedures have therefore become more popular in recent years. One reason is that smaller incisions are now used, to the extent that uni-compartmental knees are now carried out through a so-called minimally invasive approach. Still, however, in many cases this involves a 4-inch incision, significant soft tissue dissection, and significant morbidity for the patient.
To improve these procedures, various implants and techniques are being devised. One of many is disclosed in Published U.S. Patent Application 2002/0099446 A1. This reference discloses a knee-joint prosthesis comprising at least one femoral component and at least one tibial component. The femoral component includes a first portion adapted for fixable attachment to a distal end of a femur and a second portion formed with a bearing surface. The femoral component is sized so as to permit attachment to the femur of a patient without severing at least one of the cruciate ligaments. The tibial component has a first surface that is adapted to cooperate with a patient's tibia, while a second surface of the tibial component is adapted to cooperate with the femoral component. The tibial component is sized so as to permit attachment to the patients tibia without severing at least one of the cruciate ligaments.
Despite advances such as these, however, the need remains for an improved implant, preferably one that resists back-out.